The present disclosure relates generally to controllers and light modules with light emitting diodes (LEDs), and more particularly to controllers and LED modules capable of achieving high power factor and efficiency.
As well known in the art, there are different kinds of lighting fixtures developed in addition to the familiar incandescent light bulb, such as halogen lights, florescent lights and LED (light emitting diode) lights. LED lighting fixtures have several advantages. For example, LEDs have been developed to have lifespan up to 50,000 hours, about 50 times as long as a 60-watt incandescent bulb. This long lifespan makes LED lighting fixtures suitable in places where changing bulbs is difficult or expensive (e.g., hard-to-reach places, such as the exterior of buildings). Furthermore, a LED requires minute amount of electricity, having luminous efficacy about 10 times higher than an incandescent bulb and 2 times higher than a florescent light. Power consumption and conversion efficiency are big concerns in the art, and it has been a trend for LED lighting fixtures to replace several kinds of lighting fixtures.
There are several obstacles for LED lights to replace other kinds of lights, however. For example, ENERGY STAR, a joint program of the U.S. Environmental Protection Agency and the U.S. Department of Energy, requires LED light to have a power factor no less than 0.7. Furthermore, LED lighting fixtures must be cheap enough to create motivation and affordability for consumers to such replacement.
Conventional LED drivers in LED lighting fixtures first rectify an alternative-current grid power source into a direct-current power source, which is then converted into another direct-current power source with a voltage specifically suitable to drive LEDs. Each of the conventional LED drivers, as known in the art, typically needs a costly inductive device (e.g., an inductor or a transformer) and an output electrolytic capacitor (for smoothing the output voltage). Electrolytic capacitors and LEDs deteriorate greatly, however, in a hot environment. Thus, LED lighting fixtures are inevitably equipped with complex and costly heat sinkers to cool the LEDs and the electrolytic capacitors therein. That's the reason why the LED lighting fixtures with conventional LED drivers have become luxuries which will cost consumers a lot.